This invention relates generally to the field of structural fabrication and, more specifically, to a system and method for bending a structural member.
Stringers are used extensively in the aeronautic industry. A stringer is essentially a structural member used in airfoil and fuselage structures. Because stringers are used in aircraft and other aerostructures, high-cost, low-density material, such as aluminum or titanium, are used to form stringers. Since stringers are typically formed with particular bend radii, manufacturers of stringers desire cost-effective methods of forming stringers that meet tight tolerances.
Stringer forming is typically a combination of an automated and a manual process, and the quality of the bending of stringers is highly dependent on the skill and artistry of the operator. An operator uses trial-and-error before arriving at the correct set-up for a particular machine, which wastes considerable time. This trial-and-error procedure also results in wasted material, depending on how many trial-and-error cycles the operator goes through. There are usually numerous cycles the operator goes through because of various factors in bending structural members. One such factor is springback, which refers to the tendency of a material to return to its original shape when a stress is removed.
Springback is compensated for by over-bending a structural member. Typically, an operator goes through at least a few, or sometimes many, trial-and-error cycles to determine the springback for a particular structural member with a particular cross-section. In addition, stringers used in aerostructures generally have a thin cross-section, which means the structural members are more susceptible to buckling, wrinkling, and crippling. These are other factors the operator cannot determine and many trial-and-error cycles need to be performed before arriving at the correct set-up for the bending machine.
Another problem in bending stringers is that many different shapes or cross-sections of stringers are utilized depending on the aerostructure for which the stringer is used. For example, stringers may have Z-sections, C-sections, H-sections, I-sections, etc. Therefore, if a new forming machine is built for each cross-section, then considerable time and money is wasted. Thus, manufacturers desire quick, easy, and efficient ways to bend various and numerous cross-sections of stringers.
In accordance with the present invention, a system and method for bending a structural member is provided that addresses disadvantages and problems associated with previously developed systems and methods.
According to one embodiment of the invention, a system for bending a structural member includes a base, a pair of pivot plates rotationally coupled to the base, an actuator coupled between the pair of pivot plates, and a plurality of adjustable supports adjustably coupled to the pair of pivot plates. The adjustable supports are adjustable in a transverse direction, and are operable to bend the structural member through a rotation of the pivot plates.
According to another embodiment of the invention, a method for bending a structural member includes determining a plurality of support locations along a longitudinal axis of the structural member, bearing an inner pair of adjustable supports on a first side of the structural member and bearing an outer pair of adjustable supports on a second side of the structural member such that the position of the inner pair and outer pair of adjustable supports substantially match the determined plurality of support locations, and displacing the adjustable supports to a predetermined position. The adjustable supports are adjustable in a transverse direction of the structural member.
Embodiments of the invention provide numerous technical advantages. For example, a technical advantage of one embodiment of the present invention is that trial-and-error in setting up a bending apparatus is performed by a finite element analysis instead of a human, thereby eliminating guesswork and re-work of non-conforming parts, which saves considerable time and money. Another technical advantage of one embodiment of the present invention is that rapidly adjustable supports are adaptable to multiple structural member cross-sections, which saves on tooling costs as well as valuable manufacturing time.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.